This thesis is a research about the possibility of measure bioimpedance simultaneously in different body locations. It first rises a theoretical study facing the problem as a classic multichannel communication system with share channel, analysing the software and hardware problems involved for all the possibilities. The more suitable configuration chosen is based on frequency multiplexation, it consists of injecting isolated sine waves with different frequencies for each channel and uses a bandpass filter to get only the required one. About the signal processing the best option found is to record the signal using undersampling techniques and implements the filter digitally. Moreover a three channel test device has been made following the calculations for a eight channels one, in order to test the theoretical research and to find possible practical limitations. Finally this test device has been used for a concrete purpose, the breathing measuring in three points on the thorax.